Process and device for the training of human vision

ABSTRACT

The present invention concerns a process for training the visual system of a human by presenting optical stimuli to said human, said stimuli being presented to a zone within the intact visual field of said human and to a zone outside the intact visual field of said human, the latter zone comprising a zone to be trained, thereby allowing an improvement of the vision in said latter zone, said process comprising the steps of locating and defining a zone of deteriorated vision or residual visual function or partial visual system injury (“transition zone”) within the human&#39;s visual system; defining a training area which is located within said transition zone; training the human&#39;s visual system by presenting visual stimuli to the human&#39;s visual system, the majority of said visual stimuli being presented in or near said transition zone; recording changes in the characteristics of the human&#39;s visual system; adapting the location and definition of the stimulus presentation to said transition zone according to said changes; and reiterating the previous steps continuously so as to extend the human&#39;s intact visual field into said transition zone and said transition zone into a zone of more deteriorated vision or a zone of less residual visual function or a zone of substantially complete visual system injury, and a device for conducting said process.

The present invention concerns a process and device for the training ofhuman vision. In particular, the invention relates to a process andapparatus by which a change of the visual performance of persons in needof a training for improvement or completion of their vision can beaffected by stimulating their visual system with optical stimuli.

Impairments of a human's visual system may either result from anincomplete or impaired development of the visual system during infancyor from a deterioration either continuously and naturally due to ageingof the person or more or less abruptly due to diseases or accidents moreor less severely influencing the visual system. It was, for example,found that the vision of children can substantially be improved byregular sessions of training their visual system, e. g. in cases ofsquinting. On the other hand, persons whose vision was deteriorated forany reason may either stop the deteriorating development or even improvetheir vision by a specific training adapted to the cause ofdeterioration of their visual system. The present invention intends toprovide a process and device for training and improving a human's visionin all conceivable cases of impairment where the presentation of opticalstimuli to the visual system of a person having need for an improvementof the vision may promise a successful removal of the cause ofimpairment and/or increase his/her performance.

In recent years computer-technology has been utilized to train mentalfunctions of the human brain. For example, the prior art reports onmethods to treat temporal processing deficits of language-learningimpaired children using computer-training as a paradigm (M. M. Merzenichet al., Temporal processing deficits of language-learning impairedchildren ameliorated by training; Science 271, 77-81 (1996)). It is notclear, however, whether computer-based training can facilitate othersensory modalities such as visual functions after damage to the brain.

Brain injury, which may result from stroke or trauma, often impairsvisual functions. Patients typically loose sight in one half of thevisual field while the other side often remains unimpaired. This partialblindness is generally considered untreatable because it is thelong-held belief that proper vision requires a highly specific neuronalorganization (D. H. Hubel, T. N. Wiesel, Receptive fields, binocularinteraction and functional architecture in the cat's visual cortex, J.Physiol. 106-154 (1962)). Despite this specificity in neuronalorganization, there is, however, a considerable degree of plasticity inthe injured visual system (U. Eysel, O. J. Gruesser, Increasedtransneuronal excitation of the lateral geniculate nucleus after acutedifferentiation, Brain Res. 158, 107-128 (1978); J. H. Kaas et al.,Reorganization of retinotopic cortical maps in adult mammals afterlesions of the retina, Science 248, 229-231(1990); C. D. Gilbert, T. N.Wiesel, Receptive field dynamics changes in adult cerebral cortex,Nature 356,150-152 (1992)). Lost visual functions can recoverspontaneously to some extent in animals (J. Sautter, B. A. Sabel,Recovery of vision despite progressive loss of retrogradely labelledretinal ganglion cells after optic nerve crush, Europ. J. Neurosci.5,680-690 (1993); B. A. Sabel, E. Kasten, M. R. Kreutz, Recovery ofvision after partial visual system injury as a model of post-lesionneuroplasticity, Adv. Neurol. 73, 251-276 (1997); T. N. Wiesel, D. H.Hubel, Extent of recovery from the effects of visual deprivation inkittens, J. Neurophysiol. 28, 1060-1072 (1965); K. L. Chow, D. L.Steward, Reversal of structural and functional effects of long-termvisual deprivation in cats, Exp. Neurol. 34, 409-433 (1972)) and man(H. - L. L. Teuber, W. S. Battersby, M. B. Bender, Visual field defectsafter penetrating missile wounds of the brain, Cambridge, Mass., HarvardUniversity Press (1960)). At least some of this spontaneous post-lesionneuroplasticity of the adult visual system is due to extensive receptivefield reorganization following lesions in retina or cortex (U. Eysel, O.Gruesser, loc. cit.; J. H. Kaas et al.. loc. cit.).

In the prior art, training methods have been disclosed that can be usedto improve visual functions of brain damaged monkeys (A. Cowey,Perimetric study of field defects in monkeys after cortical and retinalablations, Quart. J. Exp. Psychol. 19, 232-245 (1967)) and of men (J.Zihl, Zur Behandlung von Patienten mit homonymen Gesichtsfeldstörungen,Z. Neuropsychol. 2, 95-101 (1990); E. Kasten, B. A. Sabel, Visual fieldenlargement after computer training in brain damaged patients withhomonymous deficits: an open pilot trial, Restor. Neurol. Neurosci. 8,113-127 (1995)). However, in humans it has not generally been acceptedthat training can improve vision. Nevertheless, several observationswere made that suggest that humans with visual system damage may benefitfrom visual training.

The first observation that visual training may be effective in humans isthe study by Zihl et al. (loc. cit.), who found that repeatedpresentation of visual stimuli and measurements of incrementalthresholds in the same retinal location results in small expansions ofvisual field borders in persons with visual field defects. Repeatedtesting in this situation requires, however, an experimenter to carryout the training with the person to be trained, i.e. this method cannotbe used by the person independently. Thus, it is extremely timeconsuming for both the person and the experimenter.

To overcome this manual approach of presenting visual stimuli, severaldevices have been disclosed in the prior art with which automatedtesting can be achieved. Although their efficacy has only been shown ina few individual persons and a strictly planned clinical trial was nevercarried out, there have been claims that these methods may improvevisual functions. However, because these prior art devices have been toocomplicated to use and inefficient in their application, they have notbeen widely accepted in clinical practice.

In the document No. DE-U 93 05 147 issued to Schmielau, for example, adevice for training the visual system of humans is described consistingof a large size hemispheric half bowl. Here, arrays of small light bulbsare positioned in a large diameter semicircle. Light stimuli arepresented by illuminating sequences of said light bulbs arranged closelyto each other such that they may stimulate the visual field in differentexcentricities from the center which has to be visually fixed. Whilethis device does allow assessment and training of the entire visualfield in its full extent, it has several disadvantages which precludeits widespread use. The disadvantages are (1) its size, (2) theinflexible position with which visual stimuli can be presented, and (3)the absence of any teaching of orienting the training according to theresidual visual functions. Due to the lack of presentation strategy, theuse of the Schmielau prior art device requires extended time periods. Inaddition, the half bowl used for training is inpracticable for home use.

The limitation of the Schmielau invention is apparent from the FIG. 4 ofsaid document: There, as also described in the classical text books, thevisual system of a human is shown by areas which are either intact ordeficient. There is no mention of areas of impaired, residual visualfunctions based on which a visual field training may be performed.

One may presume that computers might be useful to replace such a largesize, unpracticable device, but Schmielau (loc. cit.) states that thisis not possible.

Therefore, since it is clearly stated that computer controlled trainingis not useful for purposes of visual field training, the use ofcomputers was always refused in the prior art by those skilled in theart.

In contrast to the general expectations in the art, we have surprisinglyfound that a computer-controlled training procedure for visual functionsof a human can contribute considerably to an improvement of the trainingeffect. There was, therefore, developed a computer program which hasbeen described elsewhere (E. Kasten, B. A. Sabel, Visual fieldenlargement after computer training in brain damaged patients withhomonymous deficits: an open pilot trial. Restor. Neurol. Neurosci. 8,13-127 (1995)). The principle advantage of using a computer-controlleddevice is that it is much smaller and that it allows the continuousrecording of the person's performance. However, the programs describedby Kasten et al. (loc. cit.) present the stimuli in random order on acomputer screen, without considering the person's actual performance inthe visual task. Therefore, training has been time consuming andinefficient, though this method has been shown effective in an earlypilot study.

In the paper published by Kasten et al. (1997; loc. cit.) the programhas been described. “Sehtra”, for instance, presents small light stimuliof variable luminance in all parts of the visual field, but it does notadapt to the person's actual performance in the different field sectors.It is noted that the stimuli are presented at random by a predeterminedsector of the monitor to the person's visual field, without consideringthe actual nature of the deficit and the zone of partial Visual systeminjury or residual visual function (so-called “transition zone”).

Because of this, the persons to be trained have to respond to stimuliaddressing areas of their visual field which are, in fact, intact. As aconsequence, much time is spent by the person for purposes which areuseless therapeutically. This situation produces an unnecessary demandon the person's time and patience. Boredom and loss of motivation hastherefore often been observed.

In order to overcome this limitation, it was an object of the presentinvention to provide a process and device for the training of humanvision, which avoid the known disadvantages of the prior art. Inaddition, it was an object of the invention to provide a process anddevice for the training of human vision which take into account thetraining of zones of the person's visual system where residual visualfunctions are maintained or where the natural vision is partlydeteriorated only or where the natural vision is to be maintained on ahigh quality level (so-called “transition zones”). It was a furtherobject of the invention to provide a process and device for the trainingof human vision which allow an extension of the person's visual fieldinto said transition zone and of said transition zone into a zone ofsubstantially complete visual system injury in the case that the visionof a person is severely injured. In addition, it was an object of theinvention to provide a process and device for the training of a human'svision which may be handled not only in usual training centers under thesupervision of an experienced experimenter but also in the person'sprivate environment by himself.

Surprisingly, the above objects were achieved by the present invention.The inventors conceived a new manner by which visual stimuli arepresented on a simple device for emitting optical stimuli to the visualsystem of a human.

In a very general sense, the invention relates to a process for trainingthe visual system of a human by presenting optical stimuli to saidhuman, said stimuli being presented to a zone within the intact visualfield of said human and to a zone outside the intact visual field ofsaid human, the latter zone comprising a zone to be trained, therebyallowing an improvement of the vision in said latter zone, said processcomprising the steps of

locating and defining a zone of deteriorated vision or residual visualfunction or partial visual system injury (“transition zone”) within thehuman's visual system;

defining a training area which is located within said transition zone;

training the human visual system by presenting visual stimuli to thehuman visual system, the majority of said visual stimuli being presentedin or near said transition zone;

recording changes in the characteristics of the human's visual system;

adapting the location and definition of the stimulus presentation tosaid transition zone according to said changes; and

reiterating the previous steps continuously so as to extend the human'sintact visual field into said transition zone and said transition zoneinto a zone of more deteriorated vision or a zone of less residualvisual function or a zone of substantially complete visual systeminjury.

In a further embodiment, the invention relates to a device for trainingthe visual system or vision of a human allowing the above trainingprocess to be conducted. The device essentially comprises

a central data processing means for recording, storing, processing andemitting data from the other means of the apparatus;

at least one visual stimuli emitting means;

a fixation point means allowing the fixation of the person's view;

means for entering the person's response on visual stimuli perceived;

means for allowing a control of said at least one optical stimulipresenting means in accordance with the performance of the personresponding on optical stimuli perceived.

In a preferred embodiment of the invention, said device enables thesteps of

locating and defining a zone of deteriorated vision or residual visualfunction or partial visual system injury (“transition zone”) within thehuman's visual system;

defining a training area which is located within said transition zone;

training the human's visual system by presenting visual stimuli to thehuman's visual system, the majority of said visual stimuli beingpresented in or near said transition zone;

recording changes in the characteristics of the human's visual system;

adapting the location and definition of the stimulus presentation tosaid transition zone according to said changes; and

reiterating the previous steps continuously so as to extend the human'sintact visual field into said transition zone and said transition zoneinto a zone of more deteriorated vision or a zone of less residualvisual function or a zone of substantially complete visual systeminjury.

Thus, the inherent feature of the present invention is that the trainingby stimulus presentation predominantly occurs in or near the zone ofdeteriorated vision or the zone of residual visual function or the zoneof partial visual system injury, i. e. in the transition zone, which isthe zone intended to be trained and a presentation of stimuli in theintact visual field is considerably reduced or even avoided. Thereby,the human's vision can be improved much more efficiently than in theprior art.

With respect to these features, the present invention is different fromthe prior art process and device described by Kasten et al. (1997; loc.cit.) which does not disclose the continuous monitoring of the residualperformance of the visual system of the person to be trained. Rather,the Kasten device keeps the training area of the visual field constant,stimulating over and over again areas where vision has already beenrestored or in which vision was not at all impaired. Thus, the prior artdevice presented stimuli independent upon the persons'actualperformance. In said device, after experiencing some training benefit,the restored areas are still continuously being trained, even thoughthis is no longer required. Thus, the visual presentation paradigmdisclosed in the prior art is both laborious, time-consuming and inlarge part unnecessary. In fact, persons to be trained have reportedthat the prior art training is too long and boring.

In addition, with the prior art method it is not possible to detect andspecifically treat areas of “only” deteriorated vision or of residualvisual functions or of partial visual system injury. Because of thetime-consuming training, in the prior art process, including a trainingof areas or zones showing optimum results of visual performance, therehas been a long-felt need to conceive of a optical stimulus presentationparadigm which is shorter in duration and more efficient in its use. Inthe present invention, we have therefore conceived a visual systemtraining process and device by introducing the innovative step ofcontinuously monitoring the performance of the person in need of atraining of the visual field and stimulating only those regions of thevisual system which are “only” of deteriorated vision or partiallyinjured.

Thus, in accordance with the present invention, we developed a moreefficient approach by concentrating the visual stimulus presentations tothose areas of the visual field in which a more efficient rehabilitationprogress can be expected.

To overcome the limitation of the prior art devices, we now propose inaccordance with the invention to first locate, define and characterizethe zones of impaired, i. e. deteriorated vision or residual visualfunction or partial visual system injury. These zones of deterioratedvision or impaired vision or partial visual system injury arehereinafter shortly referred to as transition zones (see FIG. 1). Suchtransition zones may, for example, be found with aged people whosevision, for example lateral vision, becomes more and more restricted.Transition zones may also be found with people whose visual system wasinfluenced as a result of a brain injury, stroke or similar event.Another example are transition zones between zones of completelymaintained and wholly lost ability to visually discriminate betweencolours, shapes or movements. Within said transition zones, there arelocated the training areas or zones which are defined in the next stepof the present procedure.

In a preferred embodiment of the invention, the size and location ofsaid training area or areas within said transition zone are selected inaccordance with the size, location and kind of the zone of partialvisial system deterioration, of residual visual fimction or visualdeficit of said human. In other words: It has to be checked carefully,which parts of the visual system of said human have the greatest needfor the subsequent training by presenting optical stimuli.

Then, based on the individual person's performance which is determinedcontinuously or intermittently during said training, we propose topresent the training stimuli in those transition zones. In preferredembodiments of the invention, optical and preferably light stimuli arepresented to the person's visual system. It is even more preferred thatlight stimuli of different colour, luminance, intensity and/or shape arepresented to the visual system of the person to be trained. Such lightstimuli can be presented as static light stimuli or a series of lightstimuli in a sequence generating an impression of a moving object.

This “transition-zone based stimulus presentation” is based on theconsideration that there are areas of “only” deteriorated vision of aperson or partial visual functions where vision is neither intact norcompletely damaged but where some neuronal structures survived theinjury. It is reasoned that these surviving neurons, as long as theirnumber exceeds a certain minimum (“hypothesis of minimal residualstructure”), mediate the return of vision due to training, and thereforetheir stimulation by training would be the critical step to be taken. Asa consequence, to overcome the previously recognized problems ofinefficient visual field stimulation, we therefore devised a newpresentation strategy by selectively stimulating these regions(“transition zones”) using a computer-controlled stimulation device.

Specific algorithms were developed to follow the above presentationstrategy, which algorithms allow the highly efficient training of areasof visual system dysfunction or malfunction. The detailed steps of thetraining procedure are described below with respect to stimulatingspecific areas or zones of the human visual system by optical stimuli.

During the training step, changes in the characteristics of the visualsystem of the human trained are recorded. In other words: Theperformance of the person trained in view of visually recognizing theoptical stimuli presented and himself/herself presenting the desiredreaction on said visual recognition step is recorded by thesystem/device of the present invention. To give just one example: Thereaction time of the trained person on an optical stimulus presented tothe transition zone of his/her visual system is measured, and the timeelapsed between the emission of the optical stimulus and the reactiongiven (for example by pressing a button of the device), relative to anaverage time value measured before for the trained person as a base linevalue, is taken as the performance of the person with respect to thetrained area of the transition zone. However, this example is not to beconsidered as limiting the invention; any other appropriate step may betaken, too, in order to continuously or intermittently record changes inthe characteristics of the human's visual system.

Based on the continuous recordal of the changes in the characteristicsas decribed above, the location and definition of the transition zone isadapted to said changes. This may also be conducted continuously orintermittently. In other words: Depending upon the performance of thetrained person in processing the presented optical stimuli by the visualsystem, the transition zone is newly defined. Without wanting to bebound by the explanation, it can be assumed that, due to the effectivetraining of the defined transition zone, the vision of the trainedperson is improved in said transition zone, for example by improving anydeteriorated fimction of the visual system (e. g. peripheral vision,visual acuity, ability to discriminate between different colours,shapes, movement; reduction of squinting; increase of the visual angle)or improving residual visual functions or removing partial visual systeminjuries. As a result thereof, the transition zone becomes an intactarea of the person's visual system, and another part of the defectivearea may become (and is defined to be) a transition zone for anotherstep or series of steps of training by presenting optical stimuli tosaid new transition zone of the human's visual system (see also FIG. 1).

By reiterating the above-described steps, the human's intact visualfield is continuously extended into zones which were previously locatedand defined to be transition zones, and said transition zones arecontinuously extended into zones which previously were zones ofdeteriorated vision or zones of less residual visual function or zonesof substantially complete visual system injury, i. e. defective zones(see FIG. 1).

Using this computer program-based training, we conducted two independentplacebo-controlled clinical trials in humans suffering from CNS damage.While our process and device can be used for any disorder of the visualsystem without that the present study is to be considered as alimitation to such severe disorders, the persons trained and evaluatedin the present study were those with visual cortex or optic nerveinjury. We were able to show for the first time, in a strictlycontrolled clinical trial, a significant reduction of partial blindnessby training the persons'visual system through repetitive stimulation ofthe visual field, when stimulating areas of residual functions or“transition zones”.

Training Software and Training Procedure

Training was carried out with a personal computer for use at home wherepersons to be trained practiced on a regular basis. The preferredembodiment of the present invention is daily training for 1 hr in adarkened room for an extended time period, as for example a 6-monthsperiod as employed in this test. However, any other training period mayalso prove efficacious.

As the prior art devices have been inefficient, a special algorithm wasdeveloped which produced on a monitor an emission of light stimulieffecting a repetitive visual stimulation of the transition zone locatedbetween the intact and damaged visual field sector of the human to betrained. In a first step, the “transition zone” was located, defined andcharacterized. i.e. there occured a determination of the exact residualvisual function in said transition zone with respect to location, sizeand kind.

After said first step, there was defined a training area which islocated within said transition zone. Said training area is a regionwithin the transition zone where a regeneration of the neuronalstructures of the person's visual system could be expected due to theresults of the definition and characterization of the transition zone inthe first step, e. g. due to the presence of a minimum of remainingneuronal structures.

In a subsequent step, there was conducted a stimulation of the area ofimpaired function based on the performance determined in the first andsecond steps. This approach is more efficient because it does notstimulate intact areas of the visual field but just those areas whichare characterized by impaired functions.

Also, unlike prior art devices in which the program only stores the datafor a later analysis, the present invention adapts, on a continuous orintermittent basis, training algorithms to the visual system performancein or near the areas of impaired functions.

In addition, daily therapy results can be stored on suitable storingmedia like a tape or a disc which permits monitoring of compliance andwhich allows the therapy strategy to be adapted to the progress of theperson.

The invention is hereinafter described in detail with reference to theFigures. While the description of the invention mainly relates to atraining of persons whose visual system is severely damaged, all detailsof the invention, i. e. the process and the apparatus, can be appliedmutatis mutandis by a skilled person to the training of persons whosevisual system deteriorates smoothly due to an ageing of said person andals to persons whose regular vision is to be trained in order tomaintain the quality of the vision on a high level. Insofar, thedescription of the training procedure in connection to persons with aseverely damaged visual system is not to be construed as a limitation ofthe invention. In the Figures,

FIG. 1 shows an assumed visual field of a person suffering from partialblindness which visual field is divided into a sector or zone where theperson's visual functions are not impaired (“intact area”), a sector orzone of partial visual system injury (“transition zone”) and a sector orzone of substantially complete visual system injury (“defective area”).

FIG. 2 shows a computer-based high-resolution perimetry (“HRP”), whereinFIG. 2A represents the assumed visual field of a person in the form of acircle, wherein the defective area is seen on the left side (shaded halfof the circle) and the central square represents the area assessed bycomputer-based HRP; FIG. 2B represents an enlargement of the centralsquare of FIG. 2A, wherein the right white area is the zone of intactvisual function, the grey area is the area of inconsistent responses onoptical stimuli (lighter grey indicates a greater number of “hits”), andthe black area represents a zone of defective visual function; FIG. 2Cshows the enlarged left part of FIG. 2B, showing islands of residualvisual functions; FIG. 2D shows the same area as FIG. 2C, but afterrestitution training; and FIG. 2E shows the difference between FIG. 2Dand FIG. 2C in order to show an increase or decrease of visualperformance. Is is noted that the presentation of the visual stimuli isbased on the shape and location of the “grey” zones, i.e. the transitionzone where variable performance is noted. The majority of the visualstimuli are presented in this transition zone and not in the intactvisual field sector. In contrast to prior art devices, in which stimuliare presented either at random in the entire visual field or in which astimulus is moved line by line, in the present invention that stimuliare presented only in the “transition zone”.

FIG. 3 shows visual functions before (white bars) and after (black bars)restitution training or placebo (fixation training) of persons whichsustained either optic nerve or post-chiasmatic damage (mean ±SE). HRPdata are displayed as number of detected stimuli, i.e. hits, (upperpanel). The lower panel shows the position of visual field border fromzero vertical meridian in degrees of visual angle.

FIG. 4 shows data, wherein the border in HRP or TAP was determined bymeasuring the distance of the black squares (i.e. location without hits,see legend to FIG. 1) from the zero vertical meridian at the verticalposition of +20°, +10°, 0°, −10° and −20° of visual a extent of visualfield enlargement was determined by averaging these measurements andcalculating the pre-post difference. Note that the border in HRP differsfrom that obtained with TAP-perimetry.

The invention is explained in further detail with reference to theFigures and the preferred embodiments without being restricted to thesepreferred embodiments.

The computer algorithms for the step of presenting visual stimuli to thehuman's visual system are such that the monitor presents a fixationpoint, which can be presented in any part of the monitor. The fixationpoint serves to a fixation of the person's view to a certain point inorder to allow an adjustment of the person's angle of view. Insuccession, additional visual stimuli are presented in or immediatelyadjancent to the transition zone, the location of which is determined inthe previous step and changed in accordance with the person'sperformance. In the prior art device published by Kasten et al., thevisual stimuli were presented independent of the persons'actual progressand were therefore inefficient and laborious. In contrast thereto, thevisual stimuli are presented in the present invention perdominantly inor adjacent to the transition zone, i. e. an area with only a partialvisual system injury or deteriorated vision.

As in the prior art, in the present invention the person responds toeach optical stimulus to the transition zone of the visual system bypressing an appropriate key on the keyboard of the computer. In contrastto the prior art device disclosed by Kasten et al. (1997), however,there is now employed an individually adapted training procedure toincrease the probability of therapeutic benefit and training complianceby avoiding non-challenging training levels, while, at the same time,being able to reduce the total number of visual stimuli to achieve thesame effect.

It should be apparent from this disclosure that it is beneficial tolimit the area of training to those parts in the visual field which areonly partially injured or deteriorated. Of course, the actual stimuluspresented can vary in size, luminance, shape or color and it can bepresented by various means, such as a projection screen, a simplecomputer monitor or other visual projection devices such as virtualreality gargles or helmet. The type of stimulus as well as the way bywhich it is presented is not limited, as long as it is acertained thatthe location of the stimulus presentation is adapted to the personsindividual deficit and as long as the majority of the stimuluspresentations are given in “transition zones”, i.e. areas of impairedvisual functions.

The theory behind this visual field stimulation algorithm assumes thatrepetitive neuronal activitation restores functions which are otherwiselost, compromised or disused. The advantage of the present inventionover prior art devices is that by focusing the person's attention ontothe area of the visual field impairment, neuronal activation is largercompared to the prior art situation where the person has to attend to asmall light stimulus which moves along a line from the deficient to theintact area of the person's visual field. From this argument it shouldbe apparent that focusing attention to the partially injured sectors ofthe visual field would result in a relative increase of neuronalactivity by instructing the persons to focus their attention on exactlythose areas which are injured but where residual visual functions canstill be detected. It would not be of benefit to also present a greatnumber of stimuli in the intact visual field sectors.

The above argument does not mean to imply that functions in the blind orsubstantially completely defective field can never be regained, i.e. inthat zones in which previously no visual stimuli could be responded on.Rather, as our clinical trial has shown, even in those areas completelydevoid of visual functions training may restore visual function. FIGS.2C to 2E show an example. Note that areas which were previously blind(black squares in FIG. 2C) are reversed to see again after some monthsof training (white squares in FIG. 2D).

The timing of the training also does not predict how fast visual fielddeficits are restored. Whereas some persons need weeks or months forfunctions to return, in others the improvement is rapid. Therefore, thepresent invention does also not imply that training requires aparticular time period.

Another advantage of the present invention is that areas which emerge asdeficient due to the training can be specifically trained. Note in FIGS.2C to 2E areas where performance declined due to training. The prior artdevices never considered this possibility that functions can alsodecline in response to the training. Consequently, also with respect tothis fact an adaptive procedure is of benefit. Again, stimuluspresentation would be focused on those areas of the visual field whichshow deficits.

This raises the problem of how to define the area of the visual deficit.There are many ways whereby the partially injured brain area can bedefined. In theory, any lack of response to visual stimuli, an extendedreaction time to the stimuli or problems in identifying the stimuliwould qualify to define areas of visual deficits. As described in theprior art, visual deficits can be documented (a) by altered thresholdsduring testing of the visual contrast sensitivity function; (b) by areduced reaction time; or (c) by the absence of a reaction to thestimulus by the person, with or without conscienceness. Again, thepresent invention does not make any assumption as to how the deficit ofthe visual function is defined, as long as the majority of the trainingstimuli are presented in the area of the visual field which correspondsto the partially impaired function (“transition zone”).

Testing the Efficiency of the Program in Clinical Trials

The following trial—and the characteristics of the persons—is chosen todocument that the current invention is able in principle to reducevisual field defects. The examples chosen are in no way meant to implythat visual training is only effective in these and not in any otherpersons or in persons with different visual field impairment. While thepreferred embodiment is aimed at persons with lesions of the nervoussystem, the present invention may also be useful by anyone skilled inthe art to treat other disorders of the eye or visual system that do notaffect the nervous system.

In order to provide a documentation of the effectiveness of the currentinvention, we conducted two clinical trials. The persons participatingin the trials were selected from a larger pool of 130 persons witheither optic nerve injury or damage to the primary visual cortex, Theywere screened on the basis of predetermined inclusion and exclusioncriteria, and baseline assessment was carried out. The choice of theinclusion and exclusion criteria was solely selected for the purpose ofreducing performance variance within the groups of persons. They werenot selected to imply that person not fillfilling these criteria can notbe treated. In fact, the current invention is useful for any disorder ofthe visual system.

The data reported here are from two independent clinical trials with anexperimental and a control group each: In the first trial two groups,experimental and control, of optic nerve injury persons were matchedaccording to age of the person (blind conditions, n=19); in the secondtrial persons with post-chiasmatic injury were randomly assigned(double-blind, n=19). Thereafter, the persons were instructed to trainwith visual tasks on the monitor at home.

The detailed description which now follows is only one preferredembodiement of the current invention. It is not meant to be limiting,neither with respect to the kind of stimulus which is presented, nor theamount of training required nor the type of the visual system disease.It is solely meant as an illustrative example.

In HRP, 500 stimuli with luminance clearly above detection thresholdwere presented on a 17″ computer monitor (see FIG. 2) . The person wasrequired to constantly fixate on a fixation point (center star) andpress a key within 750 ms. To ensure proper fixation during hometraining, the fixation point (a star of 4 mm diameter) randomly changedits color from bright-green (95 cd/m²) to bright-yellow (100 cd/m²),whereupon the person was required to press any key within 500 ms.

White, bright stimuli were presented in succession for 150 ms duration,each at 500 different positions (25×20 grid; dark monitor screen;stimulus size (SS) 0.15°; stimulus luminance (SL) 95 cd/m²; backgroundluminance (BL) <1 cd/m²). Perimetry tasks and training were performedwith a chin support to assure a stable head position and a fixed 30 cmdistance from the monitor. The overall resolution of HRP was about fourtimes greater than that of TAP (E. Kasten, S. Wuest & B. A. Sabel, J.Clin. Exp. Neurophysiol., in press).

TAP is a static perimeter used in routine clinical practice where thevisual field up to 30° eccentricity is determined using 191 stimuli withnear threshold luminance (R. Fendrich, C. M. Wessinger, M. S. Gazzaniga,Residual vision in a scotoma: Implications for blindsight, Science 258,1489-1491 (1992)). Proper fixation of the eye was monitored using avideo camera. TAP has methodological limitations, however, because (a)the persons subjective criteria may change over time when responding tostimuli near threshold; and (b) the resolution is relatively low.Therefore, TAP performance was chos en as a secondary outcome measure.The analysis of all perimetry procedures included only values obtainedin the area in which training took place (treatment group) or anequivalent area in the placebo group. Visual acuity was measured withLandoldt ring values from which the minimal angle of resolution wascalculated. In addition, standardized catamnestic interviews wereconducted to determine whether treatment led to subjective improvementsof vision in everyday life.

Final Outcome Measures and Statistics

After 150 h (about 6 months) of training, final outcome evaluation wascarried out using the same procedures for baseline assessment. Forstatistical analysis of parametric data, a two-way ANOVA with subsequentpost-hoc comparisons was calculated for each study. Student's t-test wasused f or individual al group comparisons.

Person Selection

The trial was approved by the local medical ethics committee. Personsincluded in the study had to have both a visual field defect andpost-chiasmatic or optic nerve damage as shown by CT, MRI, surgicalrecords or ophthalmoscopic documentation of optic nerve atrophy. Personswere not entered if any one of the following exclusion criteria applied(no. of excluded cases are given in brackets):

Insufficient fixation ability (n=11);

neglect (n=1);

non-optic nerve heteronymous visual field defect (n=7);

disorders of the eye (n=9);

no residual vision (n=2);

no visual deficit (n=1);

age >75 yrs (n=4);

age <18 yrs (n=1);

died (n=2);

lesion age <12 months (n=3);

epilepsy or photosensitivity (n=2);

cognitive deficits (n=12);

not willing to participate in trial (n=27); and

no shows after initial screening (n=10).

From a total number of 130 persons screened, only 38 were entered intothe trial.

Baseline Assessment

There were no differences in the base-line characteristics between thegroups with respect to age, sex, classification of the injury or injurysize (see Table 1). After the initial screening, we obtained informedconsent, and persons attended one practice session to familiarizethemselves with the diagnostic program, “PeriMa”, (E. Kasten, H.Strasburger, B. A. Sabel, Programs for diagnosis and therapy of visualdeficits in vision rehabilitation, Spatial Vis. 10, 499-503 (1997); seeFIG. 2) and the monocular Tübinger automatic perimeter 2000 (TAP) understandardized environmental luminance conditions.

This was followed by 2 to 4 separate sessions of baseline evaluationwith HRP. The accumulated values of these repeated measures served asthe baseline value. Thereafter, the persons were assigned either to thetreatment or placebo group .

The results are shown in the subsequent Table 2 in mean ±SE. The datawere analyzed by a two-way ANOVA with post-hoc planned comparisons usingthe LSD test. F-values were taken from the two-way ANOVA with type oftraining as independent factor A and time (before and after thetraining) as dependent factor B. Significant differences are shown ascomparison to baseline # or between groups at the respective time points(§).

*p<0.05; **p<0.025; ***p<0.01.

(*) trend of p<0.10. It has to be noted that both groups differedsignificantly in the number of hits in TAP at both time points(+p<0.01).

$ These values only include the performance from the damaged half of thevisual field. ° degrees of visual angle from zero vertical meridian.

The change over baseline data were analyzed were analyzed by studentst-test.

TABLE 1 Base-line characteristics of the study participants according totreatment restitution group placebo group Characteristics (n = 19) (n =19) Age of patient (yrs) 47.7 ± 12.9 55.3 ± 16.2 Sex: male 11 13 female8 6 Classification of injury age of lesion 6.8 ± 11.4 7.2 ± 6.3post-chiasmatic injury 9 10 due to trauma 4 0 due to stroke 2 8 due toother 3 2 optic nerve atrophy 10 9 due to trauma 4 3 due to neuropathy 33 due to other 3 3 size of visual field defect in percent* ≦25 4 4 ≦50 98 ≦75 3 4 >75 3 3

TABLE 2 Diagnostic values of visual functions before and after trainingaccording to treatment groups change over baseline Baseline Finaloutcome at final outcome Characteristics restitution placeborestitution# placebo restitution placebo  F- value Post-chlasmaticinjury no. hits in HRP 97.3 ± 19.2 92.3 ± 12.0 116.9 ± 19.8* 83.4 ±11.7§*** 19.6 ± 6.2 −7.8 ± 8.5** 6.77** border position in ° 5.4 ± 1.55.1 ± 2.3 10.3 ± 1.8*** 4.2 ± 1.8§*** 4.9 ± 1.7 −0.9 ± 0.8** 9.68*** no.of misses in TAP 53.0 ± 9.1⁺ 69.2 ± 11.2 50.1 ± 9.2⁺ 71.9 ± 12.0 −2.9 ±3.0 2.7 ± 3.0 1.89 TAP border position in ° 3.51 ± 1.0 3.43 ± 0.99 3.94± 1.0 2.92 ± 0.7§*** 0.43 ± 0.3 −.51 ± .34* 3.86(*) optic nerve injuryno. hits in HRP 203.2 ± 27.8 197.7 ± 37.0 312.8 ± 24.4*** 227.8 ± 45.7109.6 ± 15.5 30.1 ± 12.7*** 15.31*** border position in ° 8.5 ± 1.8 5.8± 1.0 14.4 ± 2.4*** 10.1 ± 1.5(*) 5.8 ± 1.2 4.3 ± 0.7 0.43 no. of missesin TAP 87.9 ± 13.9 94.6 ± 17.6 63.9 ± 10.6*** 89.8 ± 15.8 −24.1 ± 3.8−4.8 ± 3.85*** 3.76(*) TAP border position in ° 3.6 ± 0.9 3.8 ± 1.2 5.7± 1.0*** 5.1 ± 1.7#** 2.1 ± 0.5 1.4 ± 0.5 0.91 acuity 21.0 ± 5.6 11.8 ±3.0 12.6 ± 2.3*** 11.9 ± 3.1 −8.4 ± 4..4 0.1 ± 1.52* 5.51*

Visual Field Enlargements

Primary outcome measure: Both restitution groups, but not the controlgroups, showed significant improvements in their ability to perceivesmall visual stimuli well above detection threshold (HRP test) after thetraining (Table 2). In the visual field sector which was trained personsreceiving restitution training responded to stimuli more frequently(hits) than the control group (post-chiasma persons: 29.4% overbaseline, optic nerve persons: 73.6%, p<0.05). In addition, controlpersons showed either no improvement (post-chiasma persons: 7.7%) orsignificantly smaller improvements (optic nerve persons: 14.4% Table 1).Optic nerve persons thus profited most from the training (FIGS. 2 and3).

The position of the visual field border was assessed before and aftertreatment as well (FIG. 4). Since in some optic nerve persons the lesionwas located on both sides of the visual field, here the border wasdetermined on both sides of the zero vertical meridian. A border shiftwas noted in both optic nerve (5.8°±1.2) and post-chiasmatic persons(4.9°±1.7), with smaller changes (optic nerve: 4.3°±0.69, n.s.) or nochanges (post-chiasma: −0.90°±0.8) in the placebo-groups. Most persons(18 out of 19) benefited from the restitution training as documented bythe primary outcome measure: For HRP, the percent improvement abovebaseline was either smaller than 20 % (n=5), up to 50% (n=5), up to 100%(n=4), or in 4 persons, above 100% (maximum in one person: 200%).

Secondary outcome measures: In optic nerve persons the area of absolutedefect as measured by TAP decreased significantly in the restitutiongroup but not in the control group. In post-chiasmatic persons there wasno such difference in TAP performance. Calculating the visual field sizeby determining the visual field border using TAP data in degrees ofvisual angle, restitution training led to a border shift, i.e. visualfield size increase, of only 0.43°±0.34in the restitution and−0.5°°±0.34decrease in the placebo group of the post-chiasmatic persons. In opticnerve persons the border shift was 2.1°±0.5 and 1.4°±0.5, respectively.

Of the 38 persons participating in the trial 30 responded to apost-trial questionnaire with which subjective improvements werechecked. 72.2% of the persons receiving restitution training (n=18) butonly 16.6% of the control group (n=12) reported subjective improvementsof vision (chi-square=8.89, p<0.003). No noteworthy differences betweenthe groups were noticed due to age or sex of the persons, the size orside (right/left) of the visual field defect and the age of the injury.

Functional Significance of Computer-Controlled Training

We have shown for the first time that visual restitution training on acomputer monitor leads to significant visual field enlargement bothafter optic nerve and visual cortex injury. Fixation training (placebo)did not increase the size of the visual field in post-chiasmaticpersons, although a small improvement was noticeable in optic nervepersons. About 95% of all the restitution group subjects experienced avisual field enlargement with a mean increase in light detection of56.4% ±12.3 above baseline and an average increase of 4.9° or 5.80° ofvisual angle in post-chiasmatic or optic nerve persons, respectively.This magnitude of change is functionally meaningful:

Firstly, a 5° increase in visual field corresponds roughly to one halfof this journal page at arms length distance, and as little as 2-3° offoveal vision are generally sufficient for reading (E. Aufhom, SozialeIntegration in Abhängigkeit von der Prognose, in: W. Hammerstein, W.Lisch (eds.), Ophthalmologische Genetik, Stuttgart (1985), pages 368 to373).

Secondly, the large majority (about 72.2%) of our persons receivingrestitution training reported subjective improvements.

The neurobiological mechanisms involved in visual restitution arecurrently unknown, but converging findings in animals and humans providesome initial clues. We propose that training reactivates survivingneuronal elements of the partially damaged structure itself, i.e. theborder region (“transition zone”) or islands of residual vision whichexist in some persons with visual cortex injury (R. Fendrich, C. M.Wessinger, M. S. Gazzaniga, Residual vision in a scotoma: Implicationsfor blindsight, Science 258, 1489-1491 (1992)). Transition zones,usually located between the intact and damaged area of the visual field(see grey areas in FIGS. 2 and 4) are proposed to be a functionalrepresentation of surviving neurons in partially injured tissue (B. A.Sabel et al (1997), loc. cit.; E. Kasten et al. (in press), loc. cit.).According to the “minimum residual structure” hypothesis (B. A. Sabel(1997), loc. cit.), survival of as little as 10-15% of neurons issufficient for recovery of vision to occur, i.e., very few residualneurons in these areas may be sufficient to reactivate visual functions(J. Sautter et al. (1993), loc. cit.). This may also explain why personswith optic nerve injury profited more from restitution training in ourtrial because their transition zones are particularly large (i.e., areasof diffuse injury, data not shown). We therefore propose that residualneurons in the partially damaged visual system which activate visualtargets only insufficiently, perhaps because of “disuse”, becomeactivated by repetitive visual stimulation during restitution training.

It is conceivable that receptive field enlargements occur which aresimilar to those shown by Kaas (J. H. Kaas et al. (1990), loc. cit.). Hefound spontaneous cortical map enlargements of 5° over the course ofseveral months in monkeys after retinal lesions, a value which is almostidentical to the 4.9°-5.8° visual field enlargement seen in our persons.Since regular visual stimulation of the damaged border region byrestitution training can significantly enlarge the visual field, theplasticity potential of the adult visual system can be utilised fortherapeutic purposes in man. The use of an in-home computerized trainingprogram is both cost-effective and convenient with no apparent sideeffects.

In conclusion, our study extends the results of previous animal studiesto humans and illustrates that persons who suffer from partial blindnessbenefit from restitution training, regaining some of their lost vision.The general implications of our findings is that computer-based trainingprograms can significantly increase human brain fimction.

What is claimed is:
 1. A process for training the visual system of ahuman by presenting optical stimuli to said human, said stimuli beingpresented to a zone within the intact visual field of said human and toa zone outside the intact visual field of said human, the latter zonecomprising a zone to be trained, thereby allowing an improvement of thevision in said latter zone, said process comprising the steps oflocating and defining a zone of deteriorated vision or residual visualfunction or partial visual system injury (“transition zone”) within thehuman's visual system; defining a training area which is located withinsaid transition zone; training the human's visual system by presentingvisual stimuli to the human's visual system, the majority of said visualstimuli being presented in or near said transition zone; recordingchanges in the characteristics of the human's visual system; adaptingthe location and definition of the stimulus presentation to saidtransition zone according to said changes; and reiterating the previoussteps continuously so as to extend the human's intact visual field intosaid transition zone and said transition zone into a zone of moredeteriorated vision or a zone of less residual visual function or a zoneof substantially complete visual system injury.
 2. The process of claim1, wherein the size, location and kind of said training area areselected in accordance with the size, location and kind of the zone ofpartial visual system deterioration, of residual visual function and/orvisual deficit of said human.
 3. The process of claim 1, wherein lightstimuli are presented to the person's visual system as the visualstimuli, preferably light stimuli of different colour, luminance,intensity and/or shape.
 4. The process of claim 1, wherein the step ofpresenting light stimuli to the person's visual system comprisespresenting a fixation point to the person's visual field allowing acontrol of the person's angle of view.
 5. The process of claim 1,wherein substantially all light stimuli are presented to the person'svisual system in or immediately adjacent to the transition zone.
 6. Theprocess of the claim 1, wherein the step of presenting light stimuli tothe person's visual system is conducted on a computer screen, on a videoscreen, on a projection screen or by visual projection devices likevirtual reality gargles or helmets.
 7. The process of claim 1, whereinthe recordal of changes in the characteristics of the person's visualsystem comprises a recordal of the responsiveness, of the colourrecognition, of the shape recognition and/or of the localization of thevisual stimuli by the person.
 8. The process of claim 1, wherein thesteps of locating and defining said transition zone, defining saidtraining area, presenting visual stimuli, recording changes in theperson's performance, adapting the location and definition of thetransition zone and reiterating the previous steps are controlled by acentral data processing means.
 9. A device for training the visualsystem or vision of a human by presenting optical stimuli to said human,being presented to a zone within the intact visual field of said humanand to a zone outside the intact visual field of said human, the latterzone comprising a zone to be trained, thereby allowing an improvement ofthe vision in said latter zone, said device comprising a central dataprocessing means for recording, storing, processing and emitting datafrom the other means of the device; at least one optical stimulipresenting means; a fixation point means allowing the fixation of theperson's view; means for entering the person's response on opticalstimuli perceived; means for allowing a control of said at least oneoptical stimuli presenting means in accordance with the performance ofthe person responding on optical stimuli perceived.
 10. The device ofclaim 9, said device enabling the steps of locating and defining a zoneof deteriorated vision or residual visual function or partial visualsystem injury (“transition zone”) within the human's visual system;defining a training area which is located within said transition zone;training the human's visual system by presenting visual stimuli to thehuman's visual system, the majority of said visual stimuli beingpresented in or near said transition zone; recording changes in thecharacteristics of the human's visual system; adapting the location anddefinition of the stimulus presentation to said transition zoneaccording to said changes; and reiterating the previous stepscontinuously so as to extend the human's intact visual field into saidtransition zone and said transition zone into a zone of moredeteriorated vision or a zone of less residual visual function or a zoneof substantially complete visual system injury.
 11. The device of claim9, additionally comprising means for fixing and/or supporting the headof the person.
 12. The device of claim 9, wherein said visualstimuli-emitting means are light emitting means, preferably lightemitting means for light of variable colour, luminance, intensity and/orshape.
 13. The device of claim 9, wherein said light emitting means is acomputer screen, a video screen, a projection screen or a visualprojection device like virtual reality gargles or helmets.
 14. Thedevice of claim 9, wherein said fixation point means allowing thefixation of the person's view is a coloured mark, preferably enabled tochange the colour in order to allow a control of the person's angle ofview.
 15. The device of claim 9, wherein said control means allows acontrol of said at least one optical stimuli presenting means inaccordance with the quality of the response on said optical stimuli. 16.The use of the device of claim 9 for training the vision of personsoperating technical machines, weapon systems or land vehicles, watervehicles and air vehicles.
 17. The use of the device of claim 9 fortraining the vision of aged persons.
 18. The use of the device of claim9 for training the vision of shortsighted or farsighted persons.
 19. Theuse of the device of claim 9 for training the vision of children,preferably squinting children.
 20. The use of the device of claim 9 fortraining the vision of persons having experienced a partial visualsystem injury.
 21. The use of the device of claim 9 to for training thevision of normal-sighted persons for maintaining the vision.